Doctors in Moscow said yesterday that the former Russian prime minister, Yegor Gaidar, had been poisoned with an unidentified toxic substance on a recent visit to Ireland, adding a new twist to the Alexander Litvinenko affair.

Mr Gaidar, an economist and one of the "young reformers" responsible for privatising Russia in the early 1990s, lost consciousness and was rushed to hospital last Friday during a conference near Dublin. Last night his daughter said she believed it was "a political poisoning". Doctors saw "no other grounds" for his sudden illness, she told the BBC's News 24.

The poisoning came a day after Mr Litvinenko, a former Russian security service officer, died in London, apparently after ingesting a radioactive isotope, polonium 210. Some public figures in Russia were quick to link the two incidents.

Mr Gaidar, 50, fainted as he was finishing a speech at the university college in Maynooth, west of the Irish capital.

A colleague, Ekaterina Genieva, told the Noviye Izvestia newspaper: "I went up to him. He was lying on the floor unconscious. There was blood coming from his nose; he was vomiting blood. This went on for more than half an hour," she said.

Mr Gaidar was flown to Moscow and is in a stable condition at an unnamed hospital. President Vladimir Putin telephoned him yesterday to wish him a speedy recovery.

The economist's spokesman, Valery Natarov, said preliminary information from doctors suggested he had not suffered from food poisoning. "They think it is a substance they cannot so far identify - it is not a natural poisoning," he said.

Mr Gaidar said he ate a fruit salad and drank a cup of tea on the day he fell ill. His family declined to comment on whether he was affected by a radioactive substance. But his daughter, Masha, who runs a political movement called Democratic Alternative, said he had lost half his weight. "He's very pale and he looks like he hasn't eaten for a week," she said.

Officials at the Russian embassy in Dublin, where Mr Gaidar stayed on Saturday night claimed that he had been suffering from gastroenteritis.

However, Mr Natarov told the Guardian that Mr Gaidar had not had medical problems before the incident. "He works so hard, travels so much, he's always on the run - he just wouldn't be able to do all that without good health."

Another of the "young reformers", Anatoly Chubais, now head of the Russian electricity monopoly Unified Energy System, linked Mr Gaidar's illness to the assassination of investigative reporter Anna Politkovskaya in Moscow in October. "It is unquestionable for me that a mortal construction of Politkovskaya, Litvinenko and Gaidar, which did not come into being by miracle, would have been exceedingly attractive for supporters of unconstitutional scenarios envisioning a change of power in Russia by force," he said.